There are mainly two types of the existing fingerprint acquisition apparatuses. One is to acquire a fingerprint by sensing a fingerprint texture directly by means of a semiconductor chip. The other is an optical fingerprint acquisition apparatus, which acquires a fingerprint image as it is formed due to differences of light intensity between a ridge and a valley when the finger touches the device surface. However, the fingerprint acquisition method based on the semiconductor chip has disadvantages of insufficient anti-static and anti-corrosion ability, and poor fingerprint acquisition sensitivity. As shown in FIG. 1, in the existing optical fingerprint and palmprint acquisition apparatus, an optical element for carrying a fingerprint and palmprint mainly include a prism 1′, a light source 2′ disposed on one side of the prism, and an image sensor 3′ and lens 4′ disposed on the other side of the prism. The vertical dimension of the prism 1′ is large, and even if other optical elements are used to carry the fingerprint, the vertical dimension of the optical lens alone is too large. Meanwhile, too many optical elements are used in most of the existing acquisition apparatuses, resulting in an overall too large vertical dimension of the acquisition apparatus.
As mentioned above, the optical fingerprint acquisition apparatus in FIG. 1 has numerous disadvantages, even if only applied to acquire a single fingerprint. However, if the optical fingerprint and palmprint acquisition apparatus is applied to acquire a palmprint, since the palmprint is significantly larger than the single fingerprint, a larger prism, and more lenses and light sensing elements are required. Because the shape and structure of the prism, the larger the surface of the prism for carrying the fingerprint or palmprint, the larger the volume of the prism. Thus, the physical dimensions of the overall fingerprint and palmprint acquisition apparatus is even larger, increasing the cost.
With the development of science and technology and the continuous increase in public security awareness, beyond the traditional security field, the fingerprint and palmprint acquisition apparatus is more and more widely used in portable electronic products, such as mobile phones, notebooks, or tablets.
With the development trend of ultra-thin electronic products, the large size of the existing optical fingerprint and palmprint acquisition apparatus makes it difficult to meet the current requirements in electronic products. On the other hand, a fingerprint and palmprint acquisition apparatus directly by a semiconductor chip cannot better meet the ultra-thin requirements in existing electronic products due to lower aesthetic design and high cost.
Therefore, how to reduce the thickness of the optical fingerprint acquisition apparatus becomes a technical problem to be solved.